Backpack



FIG. 1 is a front perspective view of a backpack showing the claimed design;

FIG. 2 is a front view thereof;

FIG. 3 is a rear view thereof;

FIG. 4 is a top view thereof;

FIG. 5 is a bottom view thereof;

FIG. 6 is a left side view thereof; and,

FIG. 7 is a right side view thereof.

The broken lines in the Figures show portions of the backpack that form no part of the claimed design.

The hatched lines in the figures show shading and not surface ornamentation. 

CLAIM The ornamental design for a backpack, as shown and described. 